This article contains a summary discussion of human health effects linked to indoor air pollution (UP) in homes and other non‐industrial environments. Rather than discussing the health effects of the many different pollutants which can be found in indoor air, the approach has been to group broad categories of adverse health effects in separate chapters, and describe the relevant indoor exposures which may give rise to these health effects. The following groups of effects have been comdered: effects on the respiratory system; allergy and other effects on the immune system; cancer and effects on reproduction: effects on the skin and mucous membranes in the eyes, nose and throat; sensory effects and other effects on the nervous system; effects on the cardiovascular system; systemic effects on the liver, kidney and gastro‐intestinal system. For each of these groups, effects associated with IAP the principal agents and sources, evidence linking IAP to the effects, susceptible groups, the public health relevance, methods for assessment, and major research needs are briefly discussed. For some groups of effects, clear relationships with exposure to IAP have been reported in the world literature. Among these are respiratory disease (particularly among children), allergy (particularly to house dust mites) and mucous membrane irritation (particularly due to formaldehyde). Large numbers of people have been, and are still being affected. Many chemicals encountered in indoor air are known or suspected to cause sensory irritation or stimulation. These, in turn, may give rise to a sense of discomfort and other symptums cummonly reported in so‐called “sick” buildings. Camplex mixtures of organic chemicals in indoor air also have the potential to invoke subtle effects on the central and peripheral nervous system, leading to changes in behaviour and performance. An increased risk of developing lung cancer has been linked to exposure to environmental tobacco smoke (ETS) and to radon decay products. Lung cancer is a very serious disease with a high fatality rate; however, the number of people affected is much lower than the number of people contracting resparatory disease or alhgies, or experiencing irritative effects due to exposure to indoor pollution. The effects of IAP on reproduction, cardiovascular disease and on other systems and organs have not been well documented to date. To a certain extent, this may mean that no serious effects occur, but there has been little by way of research to clearly document the absence of these tvpes of effects.